This study examined measurement invariance across adult self-ratings of current and retrospective childhood ADHD symptoms. A group of 265 adults (135 females and 130 males) from the general community completed ratings of their current and retrospective childhood ADHD symptoms presented in the Barkley Adult ADHD Rating Scale-IV (BAARS-IV; Barkley 2011). Initially, confirmatory factor analysis (CFA) of the both sets of ratings provided more support for a bifactor ADHD model (a model with an orthogonal general factor and specific factors for inattention [IA] and hyperactivity/impulsivity [HI]) over a 2-factor oblique model (with factors for IA and HI). Using the bifactor model, chi-square difference test indicated non-invariance for 12 factor loadings on the general factor, and 13 thresholds. Differences in approximate fit indices indicated that only 4 factor loadings were not invariant. The clinical theoretical, and psychometric implications of the findings are discussed.